MULTICAL® 302
Kamstrup A/S · Technical Description · 5512-1334_F1_GB_12.2016
41
7.6
Temperature measurement
Inlet and outlet temperatures are measured by means of an accurately matched Pt500 sensor pair. During each
temperature measurement MULTICAL
302 sends measuring current through each sensor. For Pt500 the current is
approx. 0.5 mA. Two measurements are carried out in order to suppress mains voltage picked up via sensor cables (50
Hz or 60 Hz, depending on country code). Furthermore, current measurements are made by internal reference resistors
in order to secure optimum measuring stability.
The display presents inlet and outlet temperatures as well as temperature difference in the range 0.00
°
C to 155.00
°
C.
Inlet or outlet temperatures below 0
°
C are displayed as 0.00
°
C and temperatures above 155
°
C are displayed as
155.00
°
C. When the temperature sensors are outside measuring range, Info=8 (inlet) or Info=4 (outlet) is set.
At negative temperature difference (inlet
<
outlet) the temperature difference is displayed with a negative sign and
cooling energy is calculated (provided that the meter has been configured for cooling metering).
Note
: When Info = 4 or 8, the meter's energy calculation and volume accumulation stop.
7.6.1
Measuring current and power
Measuring current is only sent through the temperature sensors during the short duration of the temperature
measurement. The effective power that is deposited in the sensor elements is thus very small, and its influence on
self-heating of the temperature sensors is less than 1/1000 K.
Pt500
Measuring current
<
0.5 mA
Measuring period
<
12 ms
Peak power
<
200
µ
W
RMS influence
("fast mode")
<
0.5
µ
W
RMS influence
("normal mode")
<
0.08
µ
W